Mandibular first molar with single root and single root canal.

Mandibular molars demonstrate considerable anatomic complexities and abnormalities with respect to number of roots and root canals. Clinicians should be aware that there is a possibility of the existence of a fewer number of roots and root canals than the normal root canal anatomy. Mandibular first molar with a single root and single canal was diagnosed with the aid of dental operating microscope and multiple angled radiographs. This case report presents a rare case of successful endodontic management of mandibular first molar with a single root and root canal.

INTRODUCTION

The mandibular first molar is the first permanent posterior tooth that erupts and is the tooth that most often requires root canal treatment.[1] This tooth usually has two roots but occasionally, it has 1/2/3 roots with 1/2/3/4 root canals in the distal root,[1] and 1/2 roots with 1/2/3/4 roots canals in the mesial root.[2] Numerous studies have noted variations in the internal anatomy of mandibular molars such as mandibular first molar with 5, 6, and 7 root canals.[2] Other rare root variations include fusion with paramolar and taurodontism.[2] However, variations can also be in the form of a lesser number of roots or canals than normal anatomy. However, the existence of single-rooted mandibular first molar is extremely rare in the dental literature. This case report describes the successful nonsurgical endodontic management of a mandibular first molar with a single root and root canal.

CASE REPORT

A 14-year-old female patient presented with the chief complaint of spontaneous toothache in her right lower back region of the jaw since 2 days. A clinical examination revealed a carious right mandibular first molar. The tooth was not mobile, and periodontal probing around the tooth was within physiological limits. Sensibility tests of the involved tooth with heated Gutta-percha (Dentsply Maillefer, Switzerland) and dry ice (R C Ice; Prime Dental Products, India) caused an intense lingering pain, whereas electronic pulp stimulation (Parkel Electronics Division, Farmingdale, New York, USA) caused an early response. A preoperative radiograph revealed occlusal radiolucency, approaching the pulp space, and break in continuity of lamina dura periapically with diffuse periapical radiolucency [Figure 1a]. From the clinical, radiographic, and sensibility tests, a diagnosis of periradicular abscess with 46 was made, and endodontic treatment was suggested to the patient.

Figure 1

(a) Preoperative radiograph. (b) Access cavity preparation showing a central canal “Cn.” (c) Working length determination radiograph

The tooth was anesthetized with 1.8 mL (30 mg) 2% lignocaine containing 1:200,000 epinephrine (Xylocaine; AstraZeneca Pharma India Ltd.). An endodontic access cavity was established. A single large canal was present at the center of the pulp chamber (named as central canal “Cn”),[3] which was confirmed using dental operating microscope (Global Surgical Corporation, St. Louis, MO, USA) under ×8 [Figure 1b]. The working length was determined with the help of an apex locator (Root ZX; Morita, Japan) and later confirmed using a radiograph [Figure 1c]. Cleaning and shaping were performed under rubber dam isolation using ProTaper nickel-titanium rotary instruments (Dentsply Maillefer) with a crown-down technique. Irrigation was performed using normal saline, 3% sodium hypochlorite solution, and 17% ethylenediaminetetraacetate; 2% chlorhexidine digluconate was used as the final irrigant. Calcium hydroxide paste was given as an intracanal medicament for 2 weeks. The canal was dried with absorbent points (Dentsply Maillefer), and snugly fitting master cone was selected [Figure 2a]. Obturation of the canal was done by a combination of warm vertical condensation and thermo plasticized injectable Gutta-percha technique (Obtura II, Obtura Corporation) [Figure 2b]. After completion of root canal treatment, the tooth was restored using posterior resin composite (P60; 3M Dental Products, St. Paul, MN, USA). The patient was asymptomatic during the follow-up period of 6 months [Figure 2c]. The patient was advised a full-coverage porcelain crown.

Figure 2

(a) Master cone selection radiograph. (b) Obturation radiograph. (c) Six months follow-up radiograph

DISCUSSION

The mandibular first molar is a frequently treated tooth and has a wide variety of root canal configurations. Variations in the morphology of the dental pulp are caused by genetic and environmental influences, and there is very definite need for clinicians to be made aware of the frequency of racially determined forms. A similar case was reported by Sooriaprakas et al. in the year 2014.[4] In the year 2011 Ioannidis et al. reported a case of endodontic management and cone-beam computed tomography (CT) evaluation of seven maxillary and mandibular molars with single roots and single canals in a patient.[5] Metgud et al. in the year 2009 reported management of a patient with a taurodont, single-rooted molars associated with multiple dental anomalies by spiral computerized tomography evaluation.[6] In 35% of cases, four canals are present.[2] The distal root contains two canals, one in the buccal and the other in the lingual position. The second distal canal is sometimes found in a separate root in the disto-lingual position. Sometimes, the “extra” canal (middle mesial canal) is found in the mesial root, which, therefore, contains three canals. In addition, cases with three canals in the distal root and two in the mesial root, two canals in the mesial root and three canals in three distal roots,[7] two canals in the disto-lingual root,[8] two roots and one canal in each,[9] four canals in mesial root of mandibular molar,[10] mandibular molar with seven canals: 2 mesiobuccal, 2 mesiolingual, and 3 distal canals were reported.[11] Gopikrishna et al., reported a case of maxillary first molar with a single root and single root canal which was identified using spiral CT.[12]

The root completion of mandibular first molar occurs at 9-10 years of age. The completion of canal differentiation begins at about 3-6 years after root completion.[9] Variations in canal anatomy are due to disturbances occurring during this canal differentiation phase. Reuben et al. in an in vitro study on mandibular first molars of the Indian population, out of 125 samples found only one sample that had a single root with a single root canal.[13]

Our case report highlights the presence of a rare anatomy in mandibular first molar having a single root and a single canal. No ex vivo studies reported the existence of mandibular first molars with a single root and a single canal. In this case, the patient did not give any history of extraction in the fourth quadrant. Thus, considering radiographically developing third molar and correlating clinically the tight contact between mandibular second premolar and molar, the tooth under consideration is mandibular right first molar [Figure 1a and b]. There were several factors, which were taken into consideration in the management of this single-rooted single canaled mandibular first molar for a better prognosis. Proper preoperative diagnosis using multiple angled radiographs and correlating them clinically is necessary. Due to large root canal space, proper removal of entire bulky pulp tissue is necessary along good biomechanical preparation in the presence of large amount of intracanal irrigation. Another challenge was obturation of this large pulpal space. The advantage of using a thermoplastized injectable obturating technique is it ensures compact obturation of the wide canals without voids. Mandibular molars bear a considerable amount of masticatory load. Being single-rooted it has a lesser area of periodontal ligament attachment, hence post endodontic management becomes critical.

CONCLUSION

The anomalies in the root canal morphology need not always be extra canals. It can also be in the form of fused or fewer canals. From a clinical standpoint, when an unusual anatomic form is encountered, multiple angled radiographs and careful inspection of the tooth under dental operating microscope will reveal more details of the anatomy of the root canal system.